Rep. Jim Cooper, D-Tenn., sees moderates in Congress as an “endangered species.” A potent combination of Congressional redistricting, retirements and campaign spending by special interests is pushing out moderate Democrats and Republicans.

WASHINGTON — While the occupant of the White House and the composition of the next Congress are still to be decided, one thing is clear: There will be many fewer moderate politicians here next year.

A potent combination of congressional redistricting, retirements of fed-up lawmakers and campaign spending by special interests is pushing out moderate members of both parties, leaving a shrinking corps of consensus builders.

Middle-of-the-road Democrats, known as Blue Dogs, have been all but eviscerated from the House over the last few elections, and now three who have been in the Republicans’ cross hairs for years are fighting uphill battles for re-election.

Among Republicans, Sen. Olympia Snowe of Maine and Rep. Steven LaTourette of Ohio, weary of partisan battles, chose to retire this year, and some, like Rep. Charles Bass of New Hampshire, have found themselves moving away from the center to survive, a technique employed by Sen. Richard Lugar of Indiana, who found it was too little too late and lost his primary campaign.

“We don’t have a Congress anymore, we have a parliament,” said Rep. Jim Cooper of Tennessee, one of the last Blue Dogs. “We moderates are an endangered species, but we are also a necessary ingredient for any problem solving.”

Reps. Larry Kissell of North Carolina, John Barrow of Georgia and Jim Matheson of Utah, all Blue Dogs, appear to be losing ground in their races for re-election. Because of redistricting, their constituencies have become less familiar with them, making them easier targets for outside groups that have been spending heavily on ads to unseat them. Their poll numbers have been dropping throughout this cycle.

Many other more moderate Democrats, including Reps. Dan Boren of Oklahoma and Mike Ross of Arkansas, and Sens. Ben Nelson of Nebraska and Kent Conrad of North Dakota, chose to hand over their member pins rather than seek re-election. In theory, the dearth of moderates means it will be even harder next year for Congress — which failed to put together even mundane measures like farm and highway legislation without a massive fight this session — to pass bills.

But Congress is facing so many potentially calamitous tax and budget issues that another theory is brewing: a combination of Democrats, once adverse to changes to entitlements, and senior Republicans may form some sort of new deal-making consensus through sheer necessity to avoid large tax increases and massive military cuts. “If Republicans think by embracing the Tea Party it is a loser politically,” said Sen. Charles Schumer of New York, the No. 3 Democrat, “it may strengthen the hands of the mainstream conservatives” to make deals with the 10 or so moderate Democrats in the Senate who are interested in reforming the Medicare program and other entitlements.

Further, there is an emerging push on the Democratic side toward the center among many of their Senate candidates, like Heidi Heitkamp in North Dakota, Joe Donnelly in Indiana, Tim Kaine in Virginia and Richard Carmona in Arizona, who all are running as pragmatic centrists willing to work with Republicans.

For this to happen, according to moderates from both parties and several congressional experts, the next president will have to make conciliation a top priority.

Arnold Schwarzenegger, the former governor of California and a moderate Republican, devoted much of his political career to beating back partisanship through a redistricting process that was removed from the hands of legislators, and pushing a nonpartisan primary process in which the top two vote getters, regardless of parties, face off in general elections. This year, both came together in his state, after years of impediments thrown up by both parties.

“These are important steps that no one wanted to take,” Schwarzenegger said. “They said, `You can’t touch that!’ It is doable if you stay in there and work with good government groups, but you have to be aware that the parties will go after you.

“Partisanship is the No. 1 enemy. We can’t move forward on the most important things plaguing our country.”

Outside groups pour loads of money into targeting candidates, particularly incumbents who are seen as disloyal to party positions, and members are pressured by groups to vote against bills that slide outside the window of party orthodoxy. “If you’re not 100 percent pure with that group or party, you’re targeted,” Boren said.

Cooper and LaTourette each recounted their extreme disappointment when they joined forces to bring a budget bill based on the recommendations of the deficit commission known as Bowles-Simpson to the House floor.

That day, both men said, they had at least 100 members of both parties with them; by the time of the evening vote, that number had been whittled to a mere 38. “Tons of people said really great things about it,” Cooper said, “but when the interest groups kicked in, they dramatically changed. One member told me his favorite lobbyist would be fired if he voted for it.”

Obama’s decision early in his presidency to allow the Democratic-controlled Congress to craft legislation like the health care law while he remained at arm’s length did not help, members on both sides said. Neither did his lack of engagement with Republicans when they were in the minority, they said.

“Obama’s biggest failing has been not reaching out to Congress,” said former Rep. Mike Castle, a moderate Republican from Delaware who lost a Senate bid two years ago. “I remember being at a White House meeting with Rahm Emanuel with other moderate Republicans,” he said, referring to the former White House chief of staff, “and the president came out and spoke to us for about 30 minutes. It was a good conversation, mostly about Medicare. I don’t know if anyone in that group ever heard from him again.”

Despite the increasing polarization, the “fiscal cliff” facing Congress at the end of the year, when a series of tax increases and steep budget cuts are set to automatically begin, may force some departing members to move more to the middle, simply because the implications are too grave.